Field of the Invention
The present invention relates to a zoom lens barrel and an optical apparatus using the same.
Description of the Related Art
A zoom lens barrel to be used for a digital camera, a video camera, or the like serving as an optical apparatus has a mechanism in which a plurality of lens units are moved by a rotation operation of a zoom ring (zoom cam ring) or the like during zooming.
Meanwhile, in a zoom lens barrel of a so-called “rear focus lens” or “inner focus lens”, in order to maintain an image forming position during zooming, it is required to appropriately drive a focus cam ring along with rotational driving of the zoom cam ring. In Japanese Patent Application Laid-Open No. 2009-151232, in order to appropriately drive a focus cam ring along with rotational driving of a zoom cam ring, the focus cam ring is engaged not only with a focus key but also with the zoom cam ring.
However, in Japanese Patent Application Laid-Open No. 2009-151232, as the zoom cam ring, in addition to a cam ring to be engaged with a zoom lens frame configured to hold zoom lens units, a cam groove to be engaged with the focus cam ring needs to be formed. Therefore, the number of cam grooves that is proportional to the number of movable units (the zoom lens units and the focus cam ring) is required in the zoom cam ring. As the number of movable units becomes larger, more space for forming the cam grooves is required in the zoom cam ring. Then, as a result, there have been problems in that a length of the zoom cam ring is increased, and that the zoom lens barrel is increased in size in an optical axis direction.